Elevator safety brake



ELEVATOR SAFETY BRAKE Filed Jan 22, 1931 ax k 2% 42 g INVENTOR wmvzssh James D l B y w /Mm Patented Aug. 29, 1933 UNITED STATES r 1,924,310 I ELEVATOR SAFETY BRAKE" James Dunlop, Park Ridge, 111., assignor to Westinghouse Electric. Elevator poration of Illinois My invention pertains to an improved elevator safety brake adapted to be carried by the elevator car, and a system of control for automatically actuating the brake to stop the car upon the occurrence of various emergency conditions.

Prior elevator safety devices have consisted of small area rail gripping jaws; or scissors grip, and actuating means for applying the jaws to'grip the railswith such a high unit area pressure that they would bite into the rails and bring the'car to' a violent stop. Not only do such devices stop the'car so suddenly that the passengers may be injured, but the apparatus itself may be damaged. In many cases the rails are scored, and the rail gripping jaws are found to be actually welded to the rails after an vice.

It is, accordingly, anobject of my invention to provide a safetybrake device which will bring the car to asmooth stop without damaging the rails and other equipment. s

It is also an object of my invention to provide a smooth acting safety braking device whichwill apply ,the brake shoes to the rails with an equalized low unit area pressure."

It is a further object of my invention toprovide f a safety braking device which may apply either a mild braking force or a strong braking force commensurate with the requirements of the emer- Another object of my invention is to provide a safety braking device having two independent actuating mechanisms. I r

A further object ofwmy invention is the 'provision of a safety braking device on acar and a speed responsive actuating device for applying the brake when the car speed exceeds a predetermined rate having associated means for Varying the predetermined Speed rate in accord which ittrips to 'rope g 'ipping position in the Well' v ance with the position of the car inthe hatch- According to my invention, ,1 provide 'a safety braking device having long; lined, brake shoes instead of the usual scissors grip or smallarea wedge safety devices.

of the drum type is provided under the car, but

it operates the brake fshoes' through'bell cranks instead of wedges as inthestandard friction safety. Independent actuating meansis provided on top of the car comprisingbiasing springs tending to lift the'shoes to-rail engaging position and electromagnetic motive means normally energized to oppose the biasing springs. A speed responsive device on the car deener'gizes the electromagnetic means and permits the brake to be 'Fig. 2 is a view of myinvention incooperative relation, the eleapplication of the safety de'. k v i vator car and its guide railsbeing Om t A standard safety plank Company, a Cor- Application January 22, 1931. Serial No. 510,445 r A 6 Claims. (01. 187-90) will best be understood from the following de scription of a specific embodiment, when read in conjunction with the accompanying drawing, 1n which: I i

wFigure 1 is a view insideelevation of an--ele-" vator system arranged in accordance with my invention; Q 7 r showing the various elements sake of'clea'rness;

Fig. 3 is anenlarg'ed line IIIIII of Fig. 1; Fig. 4 is a vertical section view taken on line IVIV as shown in Fig. 3; and s 3 Figs. 5, 6' and .7 are detail views. v v Referring more specifically to the drawingthe apparatus shown in'Fig. 1 comprises an elevator 8 car C supported by a hoist cable Ca and operable betweenguide rails 11 and 12 inthe' usual manner. A governor rope 13 passes over agovernor" sheave 14 at the top of the"hatchway and under an idler sheave 15 at the bottom of the hatchway. The rope carries a minnie ball lfi'releasably re-; ceived by a spring clip 17011 the car whereby the governor rope 13 is constrainedzto'follow the car in its movements up and down the, hatchway.

sectional'view taken on governor 18 at speeds corresponding to the speed of the car, and the governor, in turn, controls a pair of conventional rope gripping jaws l9 and 21.

known manner when the speedof the car becomes excessive. Attached to the governor rope is a safety cable 22 which is passed around-deflecting pulleys 2 3 and 24and'ree1edupona cable drum 25"which is-mounted under thef'car in a safety plank 26. The construction of the safety plank may be identical-with, the standarddrum type except that the usual rail gripping jaws or scissors grip, and the wedgeactuating members are omitted; j v r The cable drum 25 is internally threaded with right and left handed threadsto receive slidably mounted shaftsZ'l, as more clearly shown in Fig. 2. The shafts 27 pass through bearing members 29 which prevent rotation of the shafts, but-per- 110 mit them to slide freely. ,For this purpose, a h i shafts and bearings'may beof square cross-secshaft may carry a key passing loosely through corresponding keyways in the bearings, or the arms of the bell cranks 33, and are adapted to be lifted thereby when the safety cable is unreeled from the safety drum.

Brake shoes 42, of a length comparable with the height of the car, are associated with the actuatormembers 35, as shown in Figs. 3 and 4. Bars 37 are welded to the vertical stile members 38 extending the height of the car, and link members 39 are pivotally secured thereto at spaced intervals. The link members 39 may be spaced about twelve inches apart, for example, and the .to'the long brake shoe 42.

free or movable ends thereof are pivot'ally secured As shown in Figs. 3 and 4, the brake shoe 42 is supported adjacent the side of'the guide'rail 12, and when the shoe rests in its lowermost position,

the link members 39 swing back and carry it toward the bar 37 and away from the guide rail. To simplify the drawing, only-one brake shoe is shown in Figs. 3 and 4, but it is to beunderstood that a similar brake shoe is likewise mounted adjacent the opposite side of the guide rail 12, I

and a pair of. brakeshoes are similarly associated with the guide rail 11 on the other side of .the car.

It willbe apparent that when the bell cranks 33 are rotated by unreeling the safety 'cable' 22, they lift the brake shoe actuators 35, causing the rotation of the links 39 from the full-line position to the dotted-line position, as shown in Fig. 4.

I As-a consequence thereof, the brake shoes .42, will limit its downward movement.

"be projectedinto engagingrelation with their adjacent guide rails; The long brake shoes 42 may be linedwith any suitable brake lining material, whereby a smooth uniform braking pressure. will be applied.

a 5 ipendently of the safety plank 26 and its drum To permit the application of the brakes inde- 25, the upperends of the brake shoe actuators 35 pass. through bell cranks 45 disposed on the upper structure of the, elevator car; A' stop nut 46 is provided on the upper end of each actuator member 35 above the associated bell crank 45 to A concentrically disposed compresson spring 47 is provided on 7 bell crank 45.

each actuatormember just below its associated f The spring 47 reacts between the bell crank and a stop washer 48 on the actuator 35 to takeup slack motion and normally hold the actuator in its lowermost position.

Passing through the upper ends of the bell cranks 45 is a biasing rod 7 centrically disposed biasing springs 52 on the outer ends thereof. The biasing springs 52'react between the upper ends of the associated bell cranks and the stop nuts on the outer ends of the biasing rod 51, thereby applying a force tending to rock the bell cranks 45 and lift the brake shoe actuators -35. When the force of the biasing springs is unopposed, the brake shoe actuators 35 and associated brake shoes 42 are thereby lifted and the link members '39 thrust the brake shoes 42 into engaging relation with the adjacent guide rails.

In order to control the application of the brakes by the biasing springs 52, controllable means is provided on top of the car for normally applying an opposing force to the bell cranks 45.

51 which carries conj A specific mechanism suitable for this purpose comprises a torque motor 55 provided with a. portion of a split block cam actuator 56 on each end of its shaft 57 Adjacent each end of the motor shaft is a slidably mounted shaft 58 which carries the cooperating portions 59. of the split block actuators in engaging relation with those portions which are carried by the motor shaft.

of the split actuator blocks is clearly shown in" Figs. 5 and 6 from which ittwill beapparent that a motion of rotation of less than one revolution imparted to the portions carried byends of the motor shaft 57 will impart a motion of translation to each-of the cooperating blocks and slidable shafts associated therewith. An energizingcircuit extends by way of conductors 63, ,64 and toany suitable source-of excitation whereby the torque motor is normally energized "during the operation of the elevator car to continuously oppose the biasing springs 52 which are thereby rendered ineffective to lift the brake actuator bars 35 and apply the brakes, Y To deenergize the torque motor 55 and permit the application of the brake when the car overspeeds, a pair of cooperating contact members 66 and 67are interposed in the energizing circuit. One of contact members 67 .is directly, controlled by an overspeed governor 70carried by the car,

by the car may be driven at speeds corresponding to thespeed of the car up and down the hatchway, the governor shaft carries a drivingsheave 74 which engages a governor, rope 75 secured stationarily in thehatchway. As shown inFi'g. 7,

diverting sheaves 76 and 77 may be provided to hold the rope 75 in engaging relation governor sheave 74 at all times.

The energizing circuit is not'controlled solely by the movements of the contactmember 67 associated with the governor 70, but depends also with the .uponthe position of the cooperating contact member 66 which is controlledby a pivot lever arm 77. The free end of the'pivoted lever arm 77 carries a roller 78 projected into the hatchway to cooperatively engage a stationary cam '79,

which is mounted in' the hatchway adjacent the limit of travel of the car. 7 j 7 As the car approaches the end of thehatchway the roller '78 engages the cam 79,and is thereby constrained to move its contact member" 66 to the right. If the operator properly reduces the speed of the car as it approaches its limit of travel, the cooperating contact member67 associatedwith the governor 70 will also be moved to the right to maintain engagement with the cooperating contact member andfthe energizing circuit will not be interrupted. If the,

speed of tor 55 will be interrupted and the brake applied.

the car is not sufficiently diminished, the gover- It is toabe understood that a similar stationary e /m mb n m likvis b fiv d'a jacent the upper limit of travel and will operate in a similar manner to insure a safe reduction of speed as the carfapproachesiits upper limit'of travel. v 7 It is to be noted that when released, the biasing springs 52 cooperate to apply an equalized constant braking force wine brake shoes, the intensity of which .is predetermined by the adcable drumi25, an ever increasing braking force is "applied' untilthe car is stopped. The governor 70 carried by the car is preferably adjusted to set the brakes at a slower speed than is governor 18. Y

My invention is, however, most readily understood by considering an assumed operation thereof. Assuming that thecar is traveling down the hatchway at a normal rate of speed, the brakes are released and the energizingcircuit of the torque motor is maintained closed through the contact members 66 and 67.

If for some cause, such as a defective control system, or a broken hoist cable, the speed of the car increases, the governor 70 on the car will move its contact member 6'7 away from the cooperating contact member 66 thereby interupt ing the energizing circuit of the. torque motorv 55. The opposing force of the torque motor having been interrupted, the biasing springs 52 rock the bell cranks 45 inwardly to lift the brake shoe actuator members 35. As the actuators 35 are raised the links 29 thrust the lined brake shoes 42 into engaging relation with the guide rails to apply a smooth predetermined braking force and retard the car. i

If, however, the speed of the car continues to increase, the overspeed governor 18 will trip its rope-gripping jaws 19 and 21 to grip the rope 13. The "continued downward motion of the car will then be effective to unreel the safety cable 22 from the cable drum 25 causing the rotation of the latter. As the drum 25 rotates, its threaded portions project the shafts 2'7 outwardly, thereby rocking the bell cranks 33 to force the long brake shoes 42 into more forceful engagement with the guide rails. The braking effort is thereby increased until it is sufficient to stop the car, but it continues at alltimes smooth and equalized.

Assume, alternatively, that the car travels down the intermediate portions of the hatchway at a normal rate of speed in the usual manner. the car approaches the end of its hatchway, the operator, or the automatic leveling or slow down apparatus, will normally diminish the car speed properly to bring it to a safe landing. When the car has progressed within a predetermined distance of its limits of travel, the roller '78 engages the stationary cam member 79, and rotates the lever arm 77 counter-clockwise, thereby moving the associated contact member 66 to the right, If the speed of the car is properly diminished, the governor contact member 6'7 will follow up its cooperating member 66 and the energizing circuit 63, 64 and 65 of the torque motor 55 is maintained.

Assuming, however, that for some reason the car speed is not sufficiently diminished, the gover-.

nor contact 67 will not follow and maintain 'engagement with contact 66 and motor 55 will be deenergized. The opposing force being interibi 'si s i hr n .1 h -hat hwa proaches'its limit of travel.

7 1 run h oh a es r t e a tuat d rib $152M pply @pimwlhedflemiee an h ea speed wi b est? inishedf f maticallydi "f v l s? en; h for t a i h s? Uproi long o satie ake and mean or in-f ee en t f meet n h am r spons v t either the usu qr r sed ove n r 911a vern which ,i s'carried by. the ear including cooperatingmeans 9 a yi he Spe re u a io of h latter in accordance with the position of the car Although I have shown and described certain specific embodiments of invention, Iamfully aware that many modifications thereof are pos- My invention, therefore, is not .to be re-i sible. stricted except insofar as, is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention: I

1. In combination, an elevator car operable between guide rails, movable brake shoes carried by thecar, biasing means for urging the brake shoes 1 into engaging relationwith the rails, electromagnetic means effective when energized for opposing said biasing means to prevent the applicationof the brake, a circuit for energizing said electromagnetic'means when the car is operating, co-' operating contact members connected into said energizing circuit, a speed responsive device for moving a first one of said contact members away from the second contact member when the caroverspeeds, a stationary cam member mounted adjacent the end of the hatchway, cam engaging means carried by the car and associatedwith from the first contact and apply the brake if the i 7 car, speed is not sufficiently reduced as it 2. 'In combination, an elevator car operable becomparable with the height of the car, link members pivotally attached to the brake shoes and the vertical stile members of the car whereby the shoes are carried adjacent the sides of the guide rails, biasing meanscontinuously tending to lift the brake shoes whereby the linkmembers will swing them into engaging relation with the rails,

electromagnetic means effective when energized for opposing said biasing means to prevent the 'applicat-ionof the brake shoes, an energizing cirbrake to stop the car when the speed of the car exceeds a predetermined rate, and means rendered effective as the car approaches a limit of travel for gradually diminishing the speed rate at which said speed responsive means will apply the brake.

4. Incombination, an elevator car operable between guide rails, a safety brake carried by the car, a speed responsive device mounted on the car for applying said brake to stop thecar when -its speed exceeds a predetermined rate, a stationary cam member mounted adjacent the end of the hatchway, and speed regulating means carried by the, car for engaging the cam member.

in the hatchway to gradually diminish the speed rate at which the device will apply the brake as the car approaches its limit of travel. 5. In combination, an elevator car operable be said second contact members to move it away .110

tween guide rails, lined brakeshoes of a length I115 1 I 'tween guide rails, a safety brake carried by the car, means for controlling the application of the brake comprising a pair of cooperating elements for controlling the application of said brake, means for moving one of said controlling elements in accordance with the speed of the car,

means for 'moving the other controlling element in accordance with the position of the car whereby said controlling elements are normally maintained in a predetermined relative position and -means responsive to movement of one element tween guide rails, a safety'brake carried by the car,a rope stationary in the hatchway, a speed responsive device mounted on the car in engag- 7 ing relation with said rope wherebythe movement of the car up and down the hatchway drives the device at corresponding speeds, means controlled thereby for actuating the brake when the car speed exceeds a predetermined rate, an overspeed governor, a movable governor rope releasably secured to the car for driving the governor, and means controlled thereby for moving the brake to rail engaging position when the car overspeeds at an excessive rate." 7 h v JAMES 'DUNLOPJ 

